The present invention relates to a holder for a powder cartridge in a dialysis machine and in particular to safety considerations in connection with such a holder and the use of such a powder cartridge. More particularly, the present invention relates to an improved conduit layout in connection with such a holder in order to increase safety.
The term xe2x80x9cdialysis machinexe2x80x9d is intended to cover not only a machine intended for hemodialysis but also machines for hemofiltration and for hemodiafiltration, as well as for peritoneal dialysis.
European Patent Application No. 278,100 describes a dialysis machine of the type to which the present invention may be applied. This application thus describes a dialysis machine which includes a preparation unit for dialysis solutions where the preparation occurs on-line starting from concentrates in liquid and powder form positioned in separate cartridges or vessels.
A dialysis machine comprises basically two parts; namely, a first blood part for transport of blood from a patient through an extracorporeal circuit comprising a dialyzer, and a second liquid part for preparing a dialysis solution and transporting this solution to the dialyzer, and then to a drain.
The dialyzer generally comprises a semi-permeable membrane which divides the dialyzer into a blood-containing part and a dialysate-containing part. The transport of molecules and substances occurs through the membrane for conditioning the blood, in order to replace the function of the kidney.
The present invention relates to the liquid part of the dialysis machine which prepares the dialysis solution. In this part of the dialysis machine, purified water is supplied from an external source such as an RO-unit, and is mixed with concentrate in suitable proportions so that a dialysis solution is prepared. The dialysis solution comprises sodium-, bicarbonate, potassium, calcium, magnesium, chloride and acetate ions in suitable concentrations, as well as possibly glucose and other ions, all dissolved in water. The concentrations of the ions in the dialysis solution are generally mirror-images of the concentrations in blood, where the mirror line is the normal concentration in blood of the ions. Thus, if an ion concentration is increased in the blood over the normal concentration, the ion concentration in the dialysis solution is decreased in relation to the normal concentration. The pH of the solution is adjusted to about 7.1-7.4.
With the most common form of treatment occurring today, bicarbonate dialysis, the dialysis solution is prepared by mixing two liquid concentrates into the main flow of water; i.e., a B-concentrate comprising substantially bicarbonate and an A-concentrate comprising the remaining components. The B-concentrate can also contain sodium chloride. These concentrates are metered in ratios of between about 1:25 and 1:40 depending on the concentration and the desired content of the dialysate, respectively. The metering occurs either volumetrically or by measuring the conductivity and controlling metering pumps so that the correct conductivity is obtained, i.e. feedback control of the metering pumps.
The reason for the division into A- and B-concentrates is that calcium precipitates to form calcium carbonate in the presence of bicarbonate, meaning that these two substances cannot be mixed until immediately before use, and then only in low concentrations. Magnesium also causes similar problems.
European Patent Application No. 278,100 describes the use of one or more powder cartridges as a replacement for the aforementioned concentrate. The powder cartridges are coupled into the dialysis machine and water is allowed to pass through the cartridges in order to form substantially saturated solutions of the powder contents at the outlets. These saturated solutions are metered into the main flow of water instead of the above-mentioned concentrates. For a little less than 10 years, there has been a bicarbonate cartridge on the market which is sold under the trademark BiCart(copyright) by GAMBRO AB, as a replacement for the B-concentrate. The B-concentrate was the concentrate which was the most difficult to handle, since the bicarbonate solution was close to its saturation limit, and when storing in cold spaces easily formed precipitates. Additionally, containers were required which were sealed against carbon dioxide, since otherwise decomposition into sodium carbonate occurred, with subsequent pH increase.
Now there is also another type of cartridge on the market which contains sodium chloride. This cartridge replaces the larger amount of ions in the A-concentrate. The remaining ions and substances are contained in a little bag of only about half a liter, called an ion bag.
A dialysis machine which is adapted to use these three components must also have the possibility of using the still generally occurring liquid-formed concentrates. For this purpose there are two hollow rods which are removable and can be fitted into an A-concentrate canister or a B-concentrate canister, respectively. The machine then includes sensors which detect if the rods are positioned in the machine or not. Also there are separate holders for the above-mentioned cartridges. If the holders are folded out and contain a cartridge, this condition is detected by sensors.
One problem which arises with dialysis machines of this type, which are intended to be used for a plurality of different types of concentrates, is that it is possible to mix up the rods and to put the rod for the B-concentrate into the A-concentrate canister and vice versa. This error condition is detected by the electronics in the dialysis machine in that the conductivity value which is expected after the mixing-in does not occur. Thus, the conductivity for the A-concentrate is significantly higher than the conductivity for the B-concentrate.
Another potential for error is the case where the dialysis machine is provided with both cartridges of the powder type and the corresponding rod is put into a container with concentrate. In order to resolve this error condition, the liquid is taken to the bicarbonate cartridge through the rod, to the upper end of the cartridge. If the rod is put into a container with bicarbonate this has no great practical significance, and the only thing that happens is that an additional amount of bicarbonate, is dissolved in the cartridge so that the outgoing solution is substantially saturated. Normally the machine detects this in that the rotational speed for the B-metering pump is lower than when using normal B-concentrate. If, however, A-concentrate comes into a bicarbonate cartridge, gas formation (carbon dioxide) occurs which rapidly results in an alarm condition.
The same or similar conditions exist with the use of a sodium bicarbonate cartridge. If the corresponding A-rod is put into a B-canister, gas formation occurs (carbon dioxide) which rapidly results in an alarm condition.
However, the situation is different if the A-rod corresponding to the A-cartridge is put into a concentrate container containing A-concentrate. The A-concentrate contains substantially sodium chloride and in this respect the situation is the same as with bicarbonate. The A-concentrate however also contains magnesium, potassium, calcium, acetic acid and possibly glucose. Magnesium, potassium and calcium are present in only relatively small amounts, such that they do not have a noticeable effect on the conductivity measurements. If the machine is now adjusted for dialysis with a bicarbonate cartridge, a sodium chloride cartridge and a small bag containing other ions, the machine meters the necessary amount of ions from the small bag, i.e. magnesium, potassium and calcium. This means that the dialysis solution in principle contains double the amount of magnesium, potassium and calcium than was intended. Apart from the fact that this gives rise to incorrect treatment, it can be life-threatening for certain patients. A construction which makes this error condition impossible would be desirable.
One object of the present invention is to provide a dialysis machine having improved safety.
Another object of the present invention is to provide a dialysis machine which is intended for use of both liquid concentrate as well as at least one powder cartridge for sodium chloride, where it is impossible to unintentionally supply A-concentrate and at the same time use the powder cartridge.
In accordance with the present invention, these and other objects have now been realized by the invention of apparatus for the safety monitoring of a dialyzer comprising at least one holder for holding a container for a powdered substance, the holder including a supply end for supplying a liquid to the container and a delivery end for delivering the liquid containing the powdered substance from the container to a concentrate pump, the apparatus comprising a first supply conduit for supplying water to the supply end of the holder for delivery to the container, a first delivery conduit for delivering the water containing the powdered substance from the delivery end of the holder to the concentrate pump, and a second supply conduit connectable to either the delivery end of the holder or to the first delivery conduit. In a preferred embodiment, the apparatus includes a first rod connectable by the second supply conduit to the delivery end of the holder and to the first delivery conduit. In a preferred embodiment, the container includes an upper end and a lower end, the supply end of the holder comprising an upper arm for attachment to the upper end of the container and the delivery end of the holder comprising a lower arm for attachment to the lower end of the container, and wherein at least one of the upper and lower arms is movable between a first position cooperating with the second supply conduit for connecting the first rod to the concentrate pump and a second position for connecting with the delivery end of the holder. In a more preferred embodiment, the apparatus includes a flush and disinfecting conduit, and the other of the upper and lower arms is also movable between a first position cooperating with the flush and disinfection conduit and a second position.
In accordance with one embodiment of the apparatus of the present invention, the at least one holder comprises a first holder and the apparatus includes a second holder for holding a second container for a powdered substance, the second holder including a supply end for supplying a liquid to the second container and a delivery end for delivering the liquid containing the powdered substance from the second container to a second concentrate pump, and including a third holder for an ion bag.
In accordance with another embodiment of the apparatus of the present invention, the supply end of the holder comprises an upper supply arm and the delivery end of the holder comprises a lower delivery arm.
In accordance with the present invention, a method has also been devised for the safety monitoring of a dialyzer comprising at least one holder for holding a container for a powdered substance including a supply end and a delivery end, the holder including a supply end for supplying a liquid to the container and a delivery end for delivering the liquid containing the powdered substance from the container to a concentrate pump, the method comprising providing a first holder arm for the supply end of the holder and attaching the first holder arm to the supply end of the container, providing a second holder arm for the delivery end of the holder and attaching the second holder arm to the delivery end of the container, supplying a liquid substantially comprising water from a source through a first supply conduit to the supply end of the container, and delivering the liquid containing the powdered substance through a first delivery conduit to a concentrate pump from the delivery end of the container. Preferably, the method includes folding the second holder arm and connecting the folded second holder arm to a first rod for feeding the liquid containing the powdered substance through a second supply conduit directly to the first delivery conduit.
In accordance with one embodiment of the method of the present invention, the container includes an upper end and a lower end, the supply end comprising the upper end of the container and the delivery end comprising the lower end of the container.
The objects of the present invention are fulfilled by safety apparatus for a dialysis machine comprising at least one holder for a container or cartridge containing a substance in powder form. According to the present invention, the apparatus comprises a first supply conduit, which leads from a water source to a supply end of the cartridge holder, a delivery conduit for delivering solution from a delivery end of the cartridge holder to a concentrate pump, and a second supply conduit, which is connectable to the delivery end of the cartridge holder, as well as to the delivery conduit and the concentrate pump.
Preferably, the cartridge holder includes an upper holder arm intended to cooperate with an upper end of the cartridge and a lower holder arm intended to cooperate with the lower end of the cartridge, and at least one of the holder arms is maneuverable between a first position where it cooperates with the second supply conduit in order to connect the A-rod to the concentrate pump, and a second position where it cooperates with the delivery end of the cartridge. The second holder arm of the cartridge holder cooperates, in a first position, with a flush and disinfection conduit. The dialysis machine may further comprise at least one additional cartridge holder and a holder for an ion bag. Moreover, the supply end of the cartridge holder comprises an upper supply arm, and the delivery end of the cartridge holder comprises a lower delivery arm.
In another aspect of the present invention, there is provided a method of activating a safety arrangement for a dialysis machine comprising at least one holder for a cartridge containing a substance in powder form. The invention comprises the steps of: activating a first holder arm for cooperation with the supply end of the cartridge; activating a second holder arm for cooperation with the delivery end of the cartridge; supplying substantially water from a water source to the supply end of the cartridge by means of a separate first supply conduit; and delivering solution from the delivery end of the cartridge by means of a delivery conduit to a concentrate pump.
Preferably, the second holder arm is folded in for connection with an A-rod for feeding concentrate through a second supply conduit directly to the delivery conduit and the concentrate pump. The supply end is the upper end of the cartridge and the delivery end is the lower end of the cartridge.